include/asm-um/fixmap.h

   1 #ifndef __UM_FIXMAP_H
   2 #define __UM_FIXMAP_H
   3
   4 #include <linux/config.h>
   5 #include <asm/kmap_types.h>
   6
   7 /*
   8  * Here we define all the compile-time 'special' virtual
   9  * addresses. The point is to have a constant address at
  10  * compile time, but to set the physical address only
  11  * in the boot process. We allocate these special  addresses
  12  * from the end of virtual memory (0xfffff000) backwards.
  13  * Also this lets us do fail-safe vmalloc(), we
  14  * can guarantee that these special addresses and
  15  * vmalloc()-ed addresses never overlap.
  16  *
  17  * these 'compile-time allocated' memory buffers are
  18  * fixed-size 4k pages. (or larger if used with an increment
  19  * highger than 1) use fixmap_set(idx,phys) to associate
  20  * physical memory with fixmap indices.
  21  *
  22  * TLB entries of such buffers will not be flushed across
  23  * task switches.
  24  */
  25
  26 /*
  27  * on UP currently we will have no trace of the fixmap mechanizm,
  28  * no page table allocations, etc. This might change in the
  29  * future, say framebuffers for the console driver(s) could be
  30  * fix-mapped?
  31  */
  32 enum fixed_addresses {
  33 #ifdef CONFIG_HIGHMEM
  34         FIX_KMAP_BEGIN, /* reserved pte's for temporary kernel mappings */
  35         FIX_KMAP_END = FIX_KMAP_BEGIN+(KM_TYPE_NR*NR_CPUS)-1,
  36 #endif
  37         __end_of_fixed_addresses
  38 };
  39
  40 extern void __set_fixmap (enum fixed_addresses idx,
  41                           unsigned long phys, pgprot_t flags);
  42
  43 #define set_fixmap(idx, phys) \
  44                 __set_fixmap(idx, phys, PAGE_KERNEL)
  45 /*
  46  * Some hardware wants to get fixmapped without caching.
  47  */
  48 #define set_fixmap_nocache(idx, phys) \
  49                 __set_fixmap(idx, phys, PAGE_KERNEL_NOCACHE)
  50 /*
  51  * used by vmalloc.c.
  52  *
  53  * Leave one empty page between vmalloc'ed areas and
  54  * the start of the fixmap, and leave one page empty
  55  * at the top of mem..
  56  */
  57 extern unsigned long get_kmem_end(void);
  58
  59 #define FIXADDR_TOP     (get_kmem_end() - 0x2000)
  60 #define FIXADDR_SIZE    (__end_of_fixed_addresses << PAGE_SHIFT)
  61 #define FIXADDR_START   (FIXADDR_TOP - FIXADDR_SIZE)
  62
  63 #define __fix_to_virt(x)        (FIXADDR_TOP - ((x) << PAGE_SHIFT))
  64 #define __virt_to_fix(x)      ((FIXADDR_TOP - ((x)&PAGE_MASK)) >> PAGE_SHIFT)
  65
  66 extern void __this_fixmap_does_not_exist(void);
  67
  68 /*
  69  * 'index to address' translation. If anyone tries to use the idx
  70  * directly without tranlation, we catch the bug with a NULL-deference
  71  * kernel oops. Illegal ranges of incoming indices are caught too.
  72  */
  73 static inline unsigned long fix_to_virt(const unsigned int idx)
  74 {
  75         /*
  76          * this branch gets completely eliminated after inlining,
  77          * except when someone tries to use fixaddr indices in an
  78          * illegal way. (such as mixing up address types or using
  79          * out-of-range indices).
  80          *
  81          * If it doesn't get removed, the linker will complain
  82          * loudly with a reasonably clear error message..
  83          */
  84         if (idx >= __end_of_fixed_addresses)
  85                 __this_fixmap_does_not_exist();
  86
  87         return __fix_to_virt(idx);
  88 }
  89
  90 static inline unsigned long virt_to_fix(const unsigned long vaddr)
  91 {
  92       BUG_ON(vaddr >= FIXADDR_TOP || vaddr < FIXADDR_START);
  93       return __virt_to_fix(vaddr);
  94 }
  95
  96 #endif